Backport the Varnish master solution for ZERO_OBJ.

See Varnish issue 3051.

src/vmod_selector.c

@@ -41,6 +41,17 @@
 #include "vbm.h"
 #include "cache/cache_director.h"
 
+/*
+ * This is the implementation in Varnish since commit dc4a889.
+ * cf https://github.com/varnishcache/varnish-cache/issues/3051
+ */
+#undef ZERO_OBJ
+#define ZERO_OBJ(to, sz)						\
+	do {								\
+		void *(*volatile z_obj)(void *, int, size_t) = memset;	\
+		(void)z_obj(to, 0, sz);					\
+	} while (0)
+
 #include "vcc_if.h"
 #include "patricia.h"
 #include "VSC_selector.h"